I kind of think it looks more like a pre-evolution, but it's really difficult to tell from that picture. Still, at the same time, it would be weird for it to be a pre-evo with it looking so different. It's likely to just be a new forme.
It also doesn't make sense that's it's a female form, since Mewtwo is genderless.
THAT'S MISS HOME ROWED TO YOU eyes glazed like a mirror to heaven